An Eastern Airlines jet bound from Boston to Orlando on Tuesday fishtailed wildly and rolled from side-to-side while trying to escape from sudden and severe icing.

The FAA, saying the crew declared an emergency, is investigating the incident.

With the airspeed indicator and auxiliary controls iced up, the crew of Flight 601 had to battle the bucking of their Airbus 300 as it made a descent from 24,000 feet while flying over New Jersey.

''It was a bumpy ride for the passengers,'' Eastern spokeswoman Karen Ceremsak said Friday. ''In a large aircraft like that, things can get rocky. The passengers were frightened.''

None of the 142 passenger and ten crew members were injured, said Ceremsak. And she disputed an FAA claim that the crew declared an emergency.

''It was a controlled descent,'' she said. ''The pilot reported his situation and said he might have to declare an emergency. But there was not an emergency declared.''

Federal Aviation Administration spokesman Fred Farrar said the pilot of the twin-engine, wide-body jet did declare an emergency about 11 a.m., triggering a probe by agency investigators. ''We want to find out if this was an isolated incident or a problem with this type of aircraft.''

Flight 601 was flying over Snowhill, N.J., through thunderstorms that stretched from Norfolk, Va. to Philadelphia, when the plane hit an area of moisture that caused the icing, said Ceremsak.

''He knew he was approaching weather,'' she said. ''There was really no way around it. He picked the best way to go through.''

''Once he got out of the ice, everything was fine,'' said Ceremsak.

Flight 601 was a minute late arriving in Orlando, she said. The plane was taken out of service to be inspected for damage and is flying again.